The findings of the Mednick and Schulsinger studies of high risk subjects may provide a model for the understanding of the functional relationships between organic and environmental factors significant in the etiology of childhood schizophrenia. The rapid onset and recovery of autonomic response to stressful stimuli may provide a predisposition for the acquisition and generalization of avoidance responses. The relevance of the findings for the etiology of childhood schizophrenia may be clarified by an understanding of autonomic response in such groups. A survey of the literature has found it difficult to integrate the findings of previous psycho- physiological studies in severely disturbed children because of variability in diagnostic criteria, task demands, experimental methods and parameters evaluated. A prior study compared schizophrenics, MBD and normal children. The most striking finding was that of a negative habituation to stress among schizophrenic children. The comparative results were summarized within a schema which relates degrees of brain pathology to differences in arousal levels and clinical symptoms. The purpose of the proposed study is to compare GSR in autistic, schizophrenic and normal children using a replication of the Mednick procedure. Ten autistic, ten normal controls for the autistic children, ten schizophrenic children and ten normal controls for the schizophrenic children will be studied. The dependent measures will be basal levels of conductance, and frequency, latency, magnitude and recovery rate of response.